Cleaning aluminum is something I do often at work. Try this -

1. Clean with soap and water. Scrub it good with a piece of scotchbrite.

2. Rinse well.

3. Use a spray bottle to apply acid etch. The etch should get kinda foamy looking if it is working. Scrub with scotchbrite but not the same piece you used with the soap.

4. Rinse well.

If everything is clean your rinse water should run right off with no breaks. A break would mean an unclean spot and needs to be cleaned again.

I made a post awhile back on my "Ongoing project" I acid etched the whole thing before treating with alodine and starting the paint proccess.